The present disclosure relates to electrostatic charge image development toners.
In a typical electrophotographic technique, the surface of an electrostatic latent image bearing member is charged by using corona discharge etc., an electrostatic latent image is then formed by exposure using a laser etc., the electrostatic latent image is then developed by using toner to form a toner image, and the toner image is then transferred to a recording medium, resulting in a high-quality image. Toner suitable for such an electrophotography technique typically is a toner containing toner particles having an average particle size of at least 5 μm and not more than 10 μm which is produced by mixing an essential component (a binder resin), such as a thermoplastic resin, and an optional component(s) (a colorant, a charge control agent, a release agent, or a magnetic material) followed by kneading, pulverization, and classification. Such a process including kneading the components of toner, pulverizing the kneaded mixture, and classifying the pulverized matter is called a “pulverization method.” An inorganic fine powder, such as silica or titanium oxide, may be attached as an external additive to the toner particles in order to impart flowability to the toner, control charge on the toner particles, or improve the removability of the toner particles.
It is desirable that such toner have good fixability at low temperature in order to achieve energy saving or equipment downsizing. The toner having good fixability at low temperature can be satisfactorily fixed by using a fixing roller without heating the fixing roller as much as possible. However, the toner having good fixability at low temperature often contains a binder resin having a low melting point and a low glass transition point and a release agent having a low melting point. In general, when such toner is stored at high temperature, the toner particles are likely to aggregate. When the toner particles aggregate, the aggregated toner particles have charge characteristics different from those of the toner particles which are not aggregated. In this case, the aggregated toner particles may adhere to a portion which is not related to an output image, resulting in color dots occurring on a fixed output image, which is a problem.
On the other hand, an electrostatic latent image bearing member (photosensitive member) which includes a photosensitive layer of amorphous silicon, which has a high hardness, is often employed in order to reduce an environmental impact. Such a photosensitive member including the photosensitive layer having a high hardness can be used for a very long time. The photosensitive member including the photosensitive layer of amorphous silicon is used in combination with positively chargeable toner. Therefore, when the photosensitive member including the photosensitive layer of amorphous silicon is used, a compound having a positively chargeable functional group, such as a quaternary ammonium salt functional group, is typically added to toner in order to ensure that the toner will be positively charged with stability.
As such a toner, the following toner has been proposed. An external additive, which is hydrophobized with an amino group-containing compound, is attached to the surface of a toner particle which is produced by melting aggregated particulates of binder resin particulates and colorant particulates to stick together by heating. The toner particle also contains a charge control agent, such as a polymer containing a quaternary ammonium salt functional group-containing acrylate unit.